Not to get under your skin, but there are two great messages that we can learn from the skin of an Etrog (used on Sukkot as part of the Lulav & Esrog set): 

THICK SKIN

If you’ll slice up an Etrog (after Sukkot, of course) you will notice that, unlike its cousin the lemon, an Etrog fruit has much less fruit and much more rind or skin. Many Etrogim may be a third or more of rind to the fruit portion within. That’s thick skin! 

As Jews, we’re supposed to be sensitive and understanding, not tough, callous and indifferent. But there are times and situations that call for a thick-skinned Judaism, especially in college life. There may be pressures (direct or indirect) that may cause us to crack and buckle, losing our personal priorities, religious values or observance, but a thick skin could help. You don’t have to flip and flap and sway every time a wind blows this way or that, or someone says this or that, instead: hold your own, protect what you have inside, brush it all off. And believe it or not, people will actually respect you more for it. 

BUMPY SKIN & RIDGES

Lemons are much smoother than Etrogim. Bumps and ridges vary by the Etrog, but none are as smooth and flat as lemons are. Many of us would prefer a smoother life, where everything just flows and rolls in the right direction, but we learn from Etrog skins that bumpy is a better way to go. If it’s too easy, you have a lemon (think of lemons in used-cars and the like). The “beautiful fruit” that Torah refers to as the Etrog, is the fruit with its bumps and lumps, its ridges that go up and down.